The present invention is directed generally to optical data storage media and specifically to optical data storage media for small-form-factor drives.
A number of disk-shaped optical storage media have been developed for use in storing various types of digital data in a manner such that the media can be readily removed from the read/write machine or drive for which it is designed. Common current (typically read-only) examples include the compact disk (CD) and digital versatile disk (DVD). Although these examples have been highly successful for particular applications, such as storing data for use on a personal computer (PC), or storing music or other audio or video information, such as motion pictures, these devices have proved less useful in applications where, for practical, historical or other reasons, an optical storage medium with a smaller size is preferable. One class of such application includes various personal electronic devices (PEDs). Personal electronic devices in general have a size, shape and weight such that it is feasible and convenient to carry or wear such devices on the person. Typically, to be practical, such devices need to be substantially pocket-sized (e.g. no more that about 100 mm, preferably no more than about 50 mm in the longest dimension, and preferably not having any cross section that is more than about 100 mm by about 50 mm, preferably no more than about 75 mm by about 35 mm) and/or a mass of about ⅓ kg or less. Examples of personal electronic devices include digital cameras, music reproduction equipment such as small tape players with headphones or MP3 players, cellular telephones, dictating equipment, at least some types of small computers, known as personal digital assistants (PDAs), and the like.
Owing, at least in part, to the great popularity of personal electronic devices and the fact that certain personal electronic devices store (and/or utilize pre-stored) data, there is a need for a data storage system and/or medium which is compatible with at least the size and weight constraints of personal electronic devices. Various types of storage systems have been used or proposed for some or all kinds of personal electronic devices, but have proved to be less than ideal for certain applications, e.g. in terms of storage capacity, size, power consumption, data transfer, cost, and/or convenience.
By way of example only, one technique for storing images in digital cameras involves use of electronic flash cards. However, the cost to the consumer in storing one picture using such flash cards is substantial. Since one picture typically requires more than 5 megabytes of storage, the cost of storage is about $20/picture, based on current prices of these cards. Moreover, these electronic cards or media are considered nonarchival (i.e., archival memory, without refresh or similar operations, is substantially free from data loss over an extended period, such as ten years or more). Accordingly, it would be advantageous, particularly in light of the photographic film paradigm, to which many photographers are accustomed, to provide a system and archival storage medium usable in a digital camera in which the cost, to the consumer, per image or picture is reduced, e.g. compared to current electronic media used in connection with digital cameras.
For transfer of stored information to a non-PED or peripheral device, PED""s typically have a serial port. Particularly in digital cameras, the time required to transfer one or more stored images to a peripheral device via the serial port is unacceptably long. By way of example, a common serial port has a maximum data transfer rate of approximately 12 kBytes/second. A typical digital camera has more than 2 megapixels/image which equates to about 5 megabytes of uncompressed high resolution information. The time typically required to transfer the image from the digital camera via the serial port to a peripheral device will be at least 400 seconds or more.
In addition to the storage medium being configured for accommodation in a PED, it is advantageous to provide a removable medium which is sized to facilitate handling and storage by typical consumers. It is believed that there is a practical lower limit on the size of such media, e.g. since units which are too small will be susceptible to being lost or misplaced and may be difficult for consumers to handle, particularly those with limited movement or disabilities. Thus, the removable media preferably are not substantially smaller than items which are generally near the lower limit of what may readily be handled, such as coins, stamps, and the like. Accordingly, it would be advantageous to provide a removable storage medium which is not significantly smaller, in width or length, than about an inch (i.e. not significantly smaller than about 25 mm). Additionally, the removable medium is advantageously not so large that it becomes cumbersome to store or transport, and preferably is sufficiently small that it can readily be incorporated in PEDs. Accordingly it would be advantageous to provide a removable storage medium which is not significantly larger, in width or length than about 40 mm, preferably not significantly larger than about 35 mm. In contrast, the standard CD or DVD disk is about 120 mm in diameter, which is believed too large to be accommodated in a pocket-sized camera or to be, itself, considered PED-sized.
Accordingly, it would be useful to provide a data recording system which provides a removable medium, preferably archival, with a high-transfer rate, lower power consumption and large capacity, but which is sized for effective and convenient consumer use (e.g. with largest dimensions about 25-50 mm) and so as to be accommodated in relatively compact digital cameras, such as digital cameras with a size, shape and/or weight not substantially exceeding that of corresponding film cameras.
With respect to optical media types, one classification relates to their read and/or write capabilities or functions relative to information content portions of the medium. The information content portions can be generally characterized as that part of the optical medium that information is read from and/or written to. The information content portions are often, but need not be, a composite layer comprised of two or more thin films on which information is recorded (written) and/or from which information is obtained (read). According to this, optical media, or any portion thereof, can be classified as: read-only, write-once, and rewriteable. A read-only optical medium refers to a medium in which data or other information is only read from the optical medium under control of the consumer or user thereof. There is no writing or recording by the user, after the read-only optical medium has been produced or manufactured. The write-once optical medium, or any portion thereof, refers to a medium or portion thereof in which the consumer or user is able to control the recording or writing information only once on the optical medium or portion thereof. After the write-once optical medium or portion thereof has information recorded thereon by the user, the write-once optical medium is not to be written to again. That is, if a portion of the medium has been written to in which a mark is provided thereon, that portion cannot be written to again, although any other portion that does not have a mark could be written to. In one embodiment, the information content portions of the write-once optical medium can have an amorphous structure or state before recording. As part of the recording operation, the amorphous structure of the information content portions is transformed into a crystalline structure having the stored information. In one embodiment, the information layer of the write-once optical medium could also be comprised of dye-based or, alternatively, ablative materials. The rewriteable optical medium refers to a medium in which the information content portions may have information recorded thereon many times; in some cases, essentially without limit where the medium can be erased or over-written a substantial number of cycles and, in other cases, there is a finite limit where phase transition materials constitute the material structure of the medium.
With respect to a read-only optical medium, the read-only information can be provided thereon by injection molding, which results in pits or bumps being recorded as the information content portions. These indicia are indicative of recorded data or other information. Although injection molding may be preferred, such information can also be embossed. With respect to writeable (write-once, and, rewriteable) optical media, grooves are typically formed in their substrates. The grooves are utilized in locating proper positions for information to be recorded. Such information is typically recorded in the form of marks spaces, which are indicative of binary information. The marks and spaces are distinguished from each other by their different reflectivities and/or optical phase.
In accordance with known and prior art practice, each of the above-defined optical media can be further characterized as being second-surface media. In accordance with one definition, second-surface optical media can be defined in terms of the read operation that is conducted when reading information from the media. In particular, a second-surface optical medium can refer to a medium in which the read beam is incident on the substrate of the optical medium or disk before it is incident on the information layer.
The relatively thick and transparent substrate of second-surface optical media makes read-only or read-write operations relatively insensitive to dust particles, scratches and the like which are located more than 50 wavelengths from the information layer. On the other hand, the second-surface optical medium can be relatively sensitive to various opto-mechanical variations. For example, common opto-mechanical variations include: (1) tilt of the substrate relative to the optical axis; (2) substrate thickness variations; and/or (3) substrate birefringence.
These variations give rise to optical aberrations which degrade system performance arising from the presence of the thick transparent layer and which can, at least theoretically, be partially compensated for by using a suitable optical path design. Such an optical path typically can only provide compensation for a single, pre-defined thickness of the layer. Because there are likely to be variations in the thickness or other properties of the transparent layer, such compensation may be less than desired at some locations of the medium.
Because the transparent layer is typically formed from a non-conductive material, there is a further risk that rotation or similar movement of the medium will create sufficient static electrical charge that dust particles or other debris may be attracted to and may adhere to the operational surface of the medium.
Another drawback associated with second-surface optical media is that the optical requirements of such media are substantially inconsistent with the miniaturization of the disk drive and optical components for such media. As will be appreciated, a longer working distance (distance between the objective lens and the information content portions) is required for an optical system that will read information from or write information onto second-surface media. This is due to the relatively thick transparent layer through which the radiation must pass to access the recording layer. To provide the longer working distance, larger optical components (e.g., objective lens) are required.
A major contributor to on-track error rates in optical disk drive reading and writing is the improper positioning of the optical head relative to track location on the rotating disk. A xe2x80x9ctrackxe2x80x9d is a portion of the spiral or concentric data track of a typical optical disk which follows the spiral or circle for one rotation of the disk. For example, misalignment of the objective lens relative to the center of the track can cause the optical head to read information from and/or write information onto adjacent tracks. The resulting noise can reduce the signal-to-noise ratio, leading to increased error rates. This can be caused by eccentricity of the radial tracks on the disk relative to a reference or a point on the disk drive. Eccentricity or runout can result from the disk and/or tracks being positioned off-center in the disk drive and/or improper vertical alignment of the plane of the disk relative to the disk drive. It is also important to provide a high degree of concentricity on a repeatable basis. Accordingly, it would be useful to provide a method for decreasing the degree of eccentricity of the tracks relative to the disk drive and of vertical misalignment of the disk relative to the disk drive.
To achieve a small-form-factor drive, it is important to provide a medium or disk and disk cartridge having a low profile. Space is limited in combining various disk drive components for containment in the drive""s small form factor. In that regard, the optical medium or disk drive system can be characterized as having three major subsystems or components that meaningfully contribute to the total profile or height of the optical disk drive system. Generally, these major subsystems of the disk drive system contribute about equally to the total profile. These three subsystems are the height or profile of the spin motor, the optical elements and the cartridge assembly. The cartridge assembly can be defined as including the optical medium or disk, the hub assembly and the cartridge housing. Consequently, as part of providing a low profile drive, it is beneficial to provide a disk having a low profile mounting hub assembly.
In accordance with the present invention, a number of components of an optical system are provided including an optical medium or disk. The optical medium has a number of characterizing features related to being capable of storing substantial amounts of data or other information yet having a small diameter. The optical medium can be implemented as a read only-medium, a writeable medium, such as a write-once medium or a rewriteable medium, as well as combinations thereof. The optical medium can be configured to enhance power efficiency when information is written to it. The medium can be readily made and formatted, as well as being efficiently assembled with other optical system components, such as a hub assembly, cartridge assembly and optical drive.
In the preferred embodiment, the optical medium is a first-surface medium. Although it may be subject to more than one definition, in one embodiment, the first-surface optical medium refers to a medium in which the read beam during a read operation is incident on or impinges on information content portions of the first-surface optical medium before it impinges on a substrate of the first-surface optical medium. The xe2x80x9cinformation content portionsxe2x80x9d can be defined as portions of the optical medium that store or contain servo data, address data, clock data, user data, system data, as well as any other information that is provided on the optical medium. The xe2x80x9cinformation content portionsxe2x80x9d can be integral with the substrate such as the case of a read-only medium. The information content portions can also be separately provided. In such a case, the information content portions can be, for example, an information layer of a writeable medium.
In one additional or alternative definition, the first-surface optical medium can refer to an optical medium having a tangible thickness in which a read light beam during a read operation traverses less than 100 micrometers of this thickness before impinging on the information content portions.
In one embodiment, the xe2x80x9csubstratexe2x80x9d can be defined as an optical medium layer that is at least 100 micrometers (0.1 mm) in thickness. Alternatively or additionally, the substrate can also be defined as being an optical medium layer that is contiguous with the information layer. Alternatively or additionally, the substrate can also be defined as being greater in thickness than any other layer of the optical medium that has a substantially homogenous composition. In those cases in which the information layer is a composite layer or multi-film layer, these definitions may apply to a part of the composite information layer or to one or more films of the multi-film information layer.
The first-surface medium offers numerous advantages over a second-surface medium. By way of example, with first-surface medium, the radiation does not pass through the relatively thick substrate so that there is a relatively shorter optical path, in comparison with second-surface medium, thereby providing a significantly shorter working distance, in comparison with second-surface medium. Since there is a shorter working distance, a smaller objective lens diameter, for a given numerical aperture, can be utilized which results in smaller, lower mass optical components to achieve a greater degree of optical drive miniaturization. Furthermore, the first-surface medium is not sensitive to substrate birefringence and substrate thickness variations. The first-surface medium is also much less sensitive to substrate tilt.
Returning to a discussion of its structural features, the optical medium has an outer diameter of about 40 mm or less (and more typically about 35 mm or less (e.g., 32 mmxc2x110%) and a thickness of about 0.6 mm (e.g., 0.6 mmxc2x115%)). A data field, a lead out track and a lead in track are located on the optical medium. The lead-in and/or lead-out tracks contain information for servo location and for preventing over- and underscans by the optical head. The lead-out track is at a lead-out radius from a center of the optical medium. The lead-in track is located at a lead-in radius from the center of the optical medium. A data field is located between the lead-out and lead-in tracks. In one embodiment, the lead-out radius is no greater than about 6.5 mm and the lead in radius is no greater than about 16 mm. In one configuration, the lead-in track is located outwardly relative to the lead-out track (i.e., the lead out track is located closer to the disk center than the lead-in track). The small form of the medium is readily handled, transported and/or stored by consumers. The medium is sufficiently small that it may be stored in a PED (personal electronic device). In one configuration, the first-surface optical medium has an information layer with a data density of about 2.6 gigabytes per square inch of data surface for a total capacity of about 250 Megabytes per medium side.
The first-surface optical storage medium or disk has at least one (i.e. single-sided), and typically two (i.e. double-sided), information layers. Each layer can include information content mastered (ICM) data (which is typically read-only) and/or writeable areas (write-once and rewriteable). As discussed in Serial No. 60/140,633, supra, the ICM data can be provided on the optical storage medium substantially all at once. The writeable portions can be relatively long-lived and/or write-once (not rewriteable) so as to provide archival storage, and/or the techniques for forming the two areas can be substantially the same with the areas differing substantially only as to whether or not the region has content molded (or otherwise mastered) therein. For example, a molding or embossing process can be used not only for mastered content but also for formatting, sector, focus, tracking and/or test areas in the (otherwise) writeable region of the disk.
In one configuration, the disk is available for use immediately after molding or embossing procedures. This configuration constitutes a monolithic disk structure in which the optical disk does not have a coating and is not subject to secondary treatment; rather, the monolithic disk can be used as is, at least for reading information therefrom. In another embodiment, additional, later steps are provided such as applying reflective coatings to improve reflectivity, applying one or more writeable film(s), e.g., a phase change material such as TeO, GeTeSb, chalcogenide alloys or metal alloys such as InSbSn or a dye material such as cyanines or pthalcocyanines, and/or applying a protective and/or contrast enhancing coating. The ICM data or writeable areas can be on opposing or common surfaces of the optical storage medium. The medium is particularly useful at beam wavelengths preferably ranging from about 400 to about 1100 nm and more preferably from about 635 to about 675 nm when achieving data storage of about 250 Megabytes/optical medium side. In one embodiment, the optical storage medium might store read only information (e.g. audio) in a compressed format on one side thereof, while the opposing side of the medium has promotional or other commercial information, such as one or more advertisements. The format of the read only information can be based on an industry standard for such optical storage media.
The components of an optical system also include a hub assembly that is joined to the optical storage medium. The hub assembly has first and second outer surfaces. A total height of the hub assembly is defined between the first and second outer surfaces when the hub assembly is joined to the optical storage medium. When both sides of the optical storage medium are being used to store information, the ratio of the total height of the hub assembly to the thickness of the optical storage medium is at least about 1.5 and preferably greater than 2.0. In one embodiment, the hub assembly includes at least a first hub member extending away from the optical storage medium. In this embodiment, the height of the first hub member over the adjacent medium surface is at least 0.25 mm. The first hub member can be used with a second hub member, preferably when both sides of the medium are being used. Alternatively, when only one side of the medium is being used for storing information, the first hub member might be used without a second hub member. When the optical storage medium and the hub assembly, or at least the first hub member, are located in a cartridge or other housing, the hub assembly, or at least the first hub member, acts to relieve any damage that the housing might be subjected to when a compressive force or pressure is applied thereto. Relatedly, in such a case, the hub assembly, or at least the first hub member, serves to substantially reduce the likelihood that the housing will unwantedly contact the optical storage medium, or otherwise contaminate it. Additionally, in regard to achieving a low profile, the hub assembly can include rounded or curved portions that facilitate engagement between a spindle shaft and the hub assembly. The spindle shaft is part of a drive or player of the optical system. Relatedly, when the spindle engages the hub assembly in the drive, the tip of the spindle shaft enters the hub assembly a reduced or lower distance, e.g., no greater than one-half the total height of the hub assembly, when a double-sided medium is employed. A profile savings also results when unloading the hub assembly, together with and the optical storage medium, from the spindle shaft since the space required to unload the hub assembly from the spindle shaft is reduced.
With respect to more specific features, the hub assembly can include a magnetic coupling or washer that is used in joining the hub assembly to the spindle of the optical drive. The magnetic coupling is made of metal and the remaining portions of the hub assembly are typically made of plastic. The magnetic coupling is advantageous in allowing repeated loading and unloading relative to the drive without detrimental effects. Because of their different thermal coefficients of expansion, the metallic coupling is uniquely joined to the plastic hub member of the hub assembly. That is, to avoid unwanted thermal strains that might be applied by the metallic coupling to the plastic, thereby potentially resulting in damage (e.g. cracking) to the plastic hub assembly, the coupling has limited contact or engagement with the first hub member. The thickness of the magnetic coupling is a function of the desired magnetic force to be achieved. The magnetic coupling is to be connected to the spindle of the optical medium. The attractive force to the spindle depends on the thickness of the magnetic coupling, with a greater thickness resulting in a relatively greater magnetic force. After joining the magnetic coupling to the hub member, the hub assembly can then be joined to the optical medium. In one embodiment, the hub member has at least a first adhesive injection port that passes through the hub member and communicates with a channel for receiving the adhesive. The channel is located between at least portions of the first hub member and a surface of the disk. The adhesive is used to fixedly join the disk or medium to the hub assembly.
In another embodiment, the hub assembly can include the first hub member and a second hub member disposed on opposing sides of the optical medium. The first hub member engages the second hub member such that the first hub member has a surface adjacent to and spaced a distance from (or offset from) an adjacent surface of the medium to prevent damage to the medium by the first hub member when the first hub member is engaged with the second hub member.
In still another hub assembly configuration, the second hub member includes a first ring projecting outwardly from a second ring having a larger diameter than the first ring. The first and second rings are concentrically disposed about a common center. The second ring is positioned in a central hole of the medium and the first ring is received in a central bore in the first hub member to hold the first hub member in position relative to the second hub member. Accordingly, the height of the first ring above the second ring is typically no more than the height (or depth) of the central bore in the first hub member. The telescopic connection involving the central bore receiving the first ring permits the hub assembly to have a very low profile. This allows for a low loading/unloading profile for the hub assembly and the medium.
In conjunction with joining the hub assembly to the optical storage medium, it is important to eliminate, or at least substantially reduce, track runout or eccentricity. In accordance with one method to achieve this objective, a number of steps are employed. These steps include identifying for use at least a first portion of the medium that will be used for alignment purposes, i.e., properly positioning or joining of the hub assembly to the optical storage medium. The first portion is located inwardly of a peripheral edge of the medium and outwardly of a central hole in the medium. In a preferred embodiment, the first portion includes a track on the medium for storing data or other information. After at least such a first portion is identified for use, the determined position is obtained for the hub assembly. Once the determined position is obtained, the hub assembly can be positioned therein. Regarding the identifying for use step, in one embodiment, a light beam is directed against the medium and reflected light therefrom is processed to obtain the determined position. Based on this method, track runout can consistently be maintained to maximum tolerances of plus or minus 25 micrometers. As can be appreciated, conventional techniques, such as punching or molding, that determine the position of a hub based on the position of the central hole of the medium ignore the often substantial degree of eccentricity existing between the center of the hole in the medium and the positions of the radial data tracks, which typically vary from medium-to-medium. As can be further appreciated, these differences are particularly troublesome for double-sided mediums or disks that can have differently located points of track concentricity between the two sides. The method of the present invention permits the hub assembly for each medium to be centered based on actual track positions, which results in greater flexibility in compensating for manufacturing tolerances.
For double sided mediums in which the hub assembly includes first and second hub members, one located on opposing sides of the medium, the positions of the first and second hub members can be independently determined based on unique track positions located on opposing sides of the medium. Accordingly, the longitudinal center axes of the first and second hub members can be spatially offset (non-co-axial) from one another.
In an optical system, a combination comprising:
an optical medium for storing information and having a center; and
a hub assembly positioned relative to said center, said hub assembly including at least a first hub member and at least a first coupling having substantial portions located outwardly of said first hub member, said first coupling having magnetic properties.
at least a majority by volume of said hub assembly is made of plastic and said first coupling is made of metal, said plastic having a first thermal coefficient of expansion and said metal having a second thermal coefficient of expansion, wherein said first coupling is disposed relative to said first hub member in order to accommodate a difference in said first and second thermal coefficients of expansion.
a spindle to which said optical medium and said hub assembly are removably connected and in which said spindle has a tip that extends into said hub assembly no greater than one-half of a total height of said hub assembly.
said first coupling is changeable in size in a radial direction due to temperature change while maintaining alignment with said first hub member.
In an optical system, a combination comprising:
an optical medium for storing information and having a thickness and a center; and
a hub assembly positioned relative to said center and having a total height;
wherein a ratio between said total height of said hub assembly and said thickness of said optical medium is at least about 1.5.
said optical medium has a lead out track and a lead in track, said lead out track being at a lead out radius from said center of said optical medium and said lead in track being located at lead in radius from said center of said optical medium, said optical medium having a diameter and in which said diameter is no greater than about 40 mm, said thickness of said optical medium is no greater than about 0.6 mm, said lead out radius is no greater than about 6.5 mm and said lead in radius is no greater than about 16 mm.
said hub assembly has a center hole at said center thereof and also has first and second outer surfaces, with said first and second outer surfaces being located on opposite sides of said optical medium, wherein said total height of said hub assembly is defined between said first and second outer surfaces when said hub assembly is positioned relative to said center, and in which said center hole of said optical medium is substantially free of any portion of said hub assembly.
a spindle to which said optical medium and said hub assembly are removably connected and in which said spindle has a tip that extends into said hub assembly no greater than one-half of said total height of said hub assembly.
said hub assembly includes a first hub member and at least a first coupling having substantial portions located outwardly of said first hub member.
said first coupling has magnetic properties and includes at least a first tab, said first hub member has a peripheral edge and in which said first tab is positioned outwardly of portions of said peripheral edge of said first hub member.
said first hub member includes at least a first adhesive injection port for receiving adhesive to fixedly connect said first hub member to said optical medium.
said first hub member includes a channel that communicates with said first adhesive injection port.
at least a majority by volume of said hub assembly is made of plastic and said first coupling includes metal, said plastic having a first thermal coefficient of expansion and said metal having a second thermal coefficient of expansion, wherein said first coupling is disposed relative to said first hub member in order to accommodate a difference in said first and second thermal coefficients of expansion.
said first coupling is changeable in size in a radial direction due to temperature change while maintaining alignment with said first hub member.
said hub assembly includes at least a first hub member and said optical medium has an outer surface, said first hub member has a height above said outer surface that is no more than about 4 mm.
said optical medium includes at least a substrate and an information layer, and said first hub member is located more adjacent to said information layer than to said substrate.
said hub assembly has no portion located adjacent to and projecting outwardly from said substrate.
said optical medium has first and second outer surfaces and said hub assembly includes separate first and second hub members, said first hub member having a first longitudinal center axis and said second hub member having a second longitudinal center axis, said first hub member being located adjacent to said first outer surface and said second hub member being located adjacent to said second outer surface, and in which said first longitudinal center axis is offset from said second longitudinal center axis.
said hub assembly includes a first hub member and a coupling having substantial portions located outwardly of said first hub member and, when said hub assembly is joined to said optical medium, substantially all portions of said first hub member are located outwardly thereof.
said hub assembly includes a curved peripheral edge.
In an optical system, comprising a number of components including:
an optical medium for storing information and having a diameter, a thickness, a lead out track and a lead in track, said lead out track being at lead out radius from a center of said optical storage medium and said lead in track being located at a lead in radius from said center of said optical storage medium and outwardly of the lead in track, said diameter being no greater than about 40 mm, said thickness being no greater than about 0.6 mm, said lead out radius being no greater than about 6.5 mm and said lead in radius being no greater than about 16 mm.
a hub assembly fixedly connected to said optical medium and having a total height greater than said thickness of said optical medium.
said hub assembly includes at least a first hub member made substantially of plastic and a coupling made substantially of metal.
a spindle removably connected to said hub assembly and having a tip that extends no greater than one-half said total height of said hub assembly.
A hub assembly for connection to an information storage medium, comprising:
at least a first hub member being a majority by volume of plastic, said plastic having a first thermal coefficient of expansion; and
at least a first coupling including metal having a second thermal coefficient of expansion;
wherein said first coupling is disposed relative to said first hub member in order to accommodate any change in size of said first hub member due to temperature change.
said first coupling is located outwardly of said first hub member.
said first hub member has a peripheral edge and said first coupling includes a tab that is bent adjacent to said peripheral edge.
a second hub member separate from said first hub member, wherein said first hub member has a longitudinal center axis and said second hub member has a second longitudinal axis and, when said first and second hub members are joined to opposing sides of said information storage medium, said second longitudinal center axis is offset from said first longitudinal center axis.
A method for mounting a hub assembly to an information storage medium, comprising:
identifying for use at least a first portion of said information storage medium, the first portion being located inwardly of a peripheral edge of the medium and outwardly of a center of the medium;
obtaining a determined position for said hub assembly based on said identifying for use step; and
positioning said hub assembly in said determined position.
said first portion includes at least part of a track on said information storage medium.
said information storage medium has a central hole located at said center located at said center and said determined position is independent of the location of said central hole.
said identifying for use step includes contacting a peripheral edge of said information storage medium with a fixture.
contacting said information storage medium with a light beam;
directing reflected light from said information storage medium to a detector; and
processing a signal from said detector to determine the location of at least said first portion.
According to another aspect, the hub assembly for a data storage disk comprises a hub member and a raised boss near a center axis of the hub member, the raised boss being surrounded by an annular bonding surface and being configured so as to protrude into a center hole of a data storage disk when the bonding surface is in contact with a surface of the disk.
According to yet another aspect, the invention includes a combination comprising a data storage disk and two hub assemblies having raised bosses. The hub assemblies are disposed on opposite sides of the disk, the respective raised bosses of the hub assemblies protrude into a center hole of the disk, where they are bonded to each other to increase the overall bonding force between the hub assemblies and the disk. The hub assemblies and disk may be bonded together using an ultraviolet (UV) curable adhesive.
As described above, the hub assembly may include a metal washer or hub plate that is used to magnetically clamp the disk/hub assembly to the spindle of a disk drive. In one embodiment, the metal hub plate has several tabs that are bent around the disk to attach the metal hub plate to the disk. The metal hub also has features, such as notches, that are used to register the metal plate correctly with a die that is used in the process of bending the metal tabs.
The hub member may comprise a material that transmits UV radiation, e.g.,an optical grade plastic such as optical grade polycarbonate. In this embodiment, the hub member can act as a light pipe that transmits incident UV radiation to a UV curable adhesive at an interface between the hub assembly and a data storage disk or an interface with another hub assembly located on the opposite side of the disk.
The invention also includes a method of bonding a magnetic hub assembly to a data storage disk, the magnetic hub assembly comprising a UV-transmissive hub member and a metal hub plate. The method comprises applying a UV curable adhesive to a surface of least one of the hub member and a data storage disk; positioning the magnetic hub assembly against the data storage disk; and directing UV radiation into the hub member through an exposed surface of the hub member. With this method the hub member acts as a light pipe in transmitting the UV radiation to the UV curable adhesive.
Additional embodiments, together with their associated features and advantages, can be readily determined from the following description, particularly when taken together with the accompanying drawings.